1. Field of the Invention
This invention relates to a device for correcting a tremble of a focused image of an object caused by an oscillation of an optical device due to, for example, a hand tremble.
2. Description of the Related Art
Usually, a device for correcting a tremble of a focused image is mounted in an optical device, for example a camera. The correcting device is provided with angular speed sensors, which are used for detecting the tremble of an optical device. In the correcting device, an amount of the tremble is calculated, by integrating output signals output from the angular speed sensors. The correcting device is provided with a correction optical system which is included in a photographing optical system of the camera. The correction optical system is driven based on the result of calculation of the amount of the tremble, so that a movement of the focused image which is imaged on an imaging plane, for example, a film plane and an imaging plane of a photoelectric conversion element, can be corrected.
A gyro sensor is used as the angular speed sensors. An output signal of the gyro sensor is subjected to predetermined operations of electric circuits which are provided in the gyro sensor. Accordingly, there is a possibility that a null voltage is output from the gyro sensor, when the gyro sensor stands still. Namely, even if the tremble does not occur, output signal of the angular speed sensor does not reach xe2x80x9c0xe2x80x9d.
As described above, direct-current-component, for example, the null voltage and so on, is included in the output signal of the angular speed sensor. The angular speed due to the hand tremble is affected by the direct-current-component to no small extent. The direct-current-component is changed by a temperature and a time passing. Accordingly, if the output signal of the angular speed sensor is directly used for calculating an amount of the tremble, it is probable that an error is included in the result of the calculation.
In order to avoid such a problem, a CR circuit of high-pass type, which comprises a capacitor and a resistance, is connected to the gyro sensor. The direct-current-component is removed from the output signal of the angular speed sensor by the CR circuit, so that an output signal corresponding to only the angular speed can be obtained. Further, the above-mentioned null voltage is also removed by the CR circuit.
In the CR circuit, a cut-off-frequency is determined by a time instant of the CR circuit. In other words, the time instant is set in accordance with the cut-off-frequency. On the other hand, it takes a predetermined time to finish removing the null voltage, in accordance with the time instant.
In the camera which is provided with the correcting device, a photographing operation is started after the removal of the null voltage is finished. Accordingly, there is a problem of missing a photographing opportunity. Further, if the photographing operation is started before the null voltage is completely removed, there is another problem that the accuracy of the tremble correction is lowered due to a remaining null voltage.
Therefore, an object of the present invention is to provide a device for correcting the focused image tremble, in which an accurate correction of the focused image tremble is able to be performed immediately after the device begins to be operated. Another object of the present invention is to provide a camera, provided with the correcting device.
In accordance with an aspect of the present invention, there is provided a device for correcting a tremble of a focused image comprising: a plurality of tremble detectors that detect a tremble of an optical axis of an optical device; a correction optical system that corrects the tremble; driving devices that drive the correction optical system; a controlling system that controls the driving devices such that the correction optical system is driven in order to cancel a focused image tremble of an object due to the tremble of the optical axis; direct-current-component removing systems that respectively output a signal obtained by removing a direct-current-component from an output signal which is output from a corresponding tremble detector of the tremble detectors; and tremble-detection initializing systems that respectively initialize the output signal of the corresponding tremble detector.
Each of the direct-current-component removing systems includes: a circuit element that has a predetermined resistance value; a capacitor; and a difference amplifier that outputs a difference between an input signal input from a first signal line that is connected to the corresponding tremble detector and an input signal input from a second signal line that is connected to the corresponding tremble detector through the circuit element and the capacitor. Each of the tremble-detection initializing systems short-circuits the circuit element and connects only the capacitor in the second signal line.
Each of the direct-current-component removing systems includes a cut-off-frequency changing system that changes a frequency of a frequency component removed from the output signal.
Each of the direct-current-component removing systems includes: a first resistance that is connectable between the corresponding tremble detector and the capacitor; and a second resistance, having a resistance value which is greater than that of the first resistance, that is connectable between the corresponding tremble detector and the capacitor. Each of the tremble-detection initializing systems includes a first switch system by which the corresponding tremble detector and the capacitor are connected in series. The cut-off-frequency changing system includes: a second switch system that connects the first resistance between the corresponding tremble detector and the capacitor; and a third switch system that connects the second resistance between the corresponding tremble detector and the capacitor.
In the second signal line, the first resistance and the capacitor are connected in series, and the second resistance and the capacitor are connected in series. Further, in the second signal line, the first switch system; the second switch system and the first resistance; and the third switch system and the second resistance are connected in parallel. When the first switch system is closed and the second switch system and the third switch system are opened, the output signal is initialized by the difference amplifier. Immediately after an electric power is supplied to the optical device, only the first switch system is closed.
In accordance with another aspect of the present invention, there is provided a device for correcting a tremble of a focused image comprising: a plurality of tremble detectors that detect a tremble of an optical axis of an optical device; a correction optical system that corrects the tremble; driving devices that drive the correction optical system; a controlling system that controls the driving devices such that the correction optical system is driven in order to cancel a focused image tremble of an object due to the tremble of the optical axis; and difference amplifiers that respectively outputs a difference between an input signal input from a first signal line that is connected to a corresponding tremble detector of the tremble detectors and an input signal input from a second signal line that is connected to the corresponding tremble detector through a circuit element and a capacitor. When the circuit element is short-circuited and the capacitor and the corresponding tremble detector are connected in series, an output signal of the corresponding tremble detector is initialized by a corresponding difference amplifier of the difference amplifiers.
In accordance with another aspect of the present invention, there is provided a camera which is provided with a device for correcting a tremble of a focused image comprising: a photographing optical system; tremble detectors that detect a tremble of an optical axis of the photographing optical system; a correction optical system that corrects the tremble of the optical axis, being provided for the tremble correcting device so as to be included in the photographing optical system; driving devices that drive the correction optical system; a photographing controlling system that controls an image capturing operation to record an image of the object; and a tremble correction controlling system that controls the driving device such that a focused image tremble of an object due to the tremble of the optical axis can be canceled; direct-current-component removing systems that respectively output a signal obtained by removing a direct-current-component from an output signal which is output from a corresponding tremble detector of the tremble detectors; and removing system controllers that respectively initialize the output signal of the corresponding tremble detector.
Each of the direct-current-component removing systems includes: a circuit element that has a predetermined resistance value; a capacitor; and a difference amplifier that outputs a difference between an input signal input from a first signal line that is connected to a corresponding tremble detector of the tremble detectors and an input signal input from a second signal line that is connected to the corresponding tremble detector through the circuit element and the capacitor. Each of the tremble-detection initializing systems short-circuits the circuit element and connects only the capacitor in the second signal line.
Each of the direct-current-component removing systems includes a cut-off-frequency changing system that changes a frequency of a frequency component removed from the output signal.
Each of the direct-current-component removing systems includes: a first resistance that is connectable between the corresponding tremble detector and the capacitor; and a second resistance, having a resistance value which is greater than that of the first resistance, that is connectable between the corresponding tremble detector and the capacitor. Each of the tremble-detection initializing systems includes a first switch system by which the corresponding tremble detector and the capacitor are connected in series. The cut-off-frequency changing system includes: a second switch system that connects the first resistance between the corresponding tremble detector and the capacitor; and a third switch system that connects the second resistance between the corresponding tremble detector and the capacitor.
In the second signal line, the first resistance and the capacitor are connected in series, the second resistance and the capacitor are connected in series. Further, in the second signal line, the first switch system; the second switch system and the first resistance; and the third switch system and the second resistance are connected in parallel. Immediately after an electric power is supplied to the camera, only the first switch system is closed; during a photometry operation, only the second switch system is closed; and while the image capturing operation is carried out, only the third switch system is closed.